FR2696372A1 - Thermally-sensitive, low-rigidity recording material - made from backing layer, e.g. of synthetic paper, with thin coating of thermally-sensitive substance - Google Patents

Abstract

The material is made from a backing layer, e.g. of paper, and a coating of a thermally sensitive colouring substance which is capable of changing colour when heat is applied to it. The rigidity of the coating substance is less than a specified limit when measured in a lengthwise direction, i.e. in line with the cellulose fibres of the backing material, or in a specified direction when the backing material contains no fibres. The thickness of the coating layer is 150 micrometres or less, and the backing material is preferably of a synthetic paper with polyethylene, polypropylene, polystyrene or PVC as its main constituent. Where it is made from plastic film it should be of low-density polyethylene or PVC, with a relatively low module of elasticity. The thermally sensitive coating can be made by mixing two liquids in a 1:3 ratio. The first liquid can comprise (parts by weight): 3-(N-methyl-N-cyclohexyl)amino-6-methyl-7-anilino-fluorane 10; 10 per cent polyvinyl alcohol solution 10; water 80. The second liquid can comprise: p-hydroxybenzyl benzoate 10; calcium carbonate 10; 2,2'-methylenebis (4-methyl-6-tert-butylphenol) 5; 10 per cent aqueous polyvinyl alcohol solution 20; water 55. ADVANTAGE - Rapid image recording without sound or environmental pollution, and lower manufacturing costs.

Description

The present invention relates to a thermo recording material.

  sensitive capable of coloring to form colored images when

heat is applied to it.

  In general, a heat-sensitive recording material consists of a support, such as a sheet of paper or of synthetic paper or a plastic film, on which is placed a heat-sensitive coloring layer, the main component of which is a heat-sensitive coloring composition. heat-sensitive recording can produce a colored image when heat is applied to it using a thermal head, thermal pencil,

  a laser beam or a strobe light.

  This type of heat-sensitive recording material is widely used, not only as a recording material for copying books and documents, but also as a recording material usable in

  printers of electronic calculators, facsimile machines, devices

  Reels of selling tickets and label recorders because it has the following advantages over conventional recording materials: (1) Recording an image can be accomplished quickly at

  relatively simple device without complicated development steps

  ment and fixing of images; (2) image recording can be accomplished without noise and without environmental pollution; and

  (3) manufacturing costs are low.

  The heat-sensitive coloring composition for use in the heat-sensitive recording material comprises a coloring agent and a color developer capable of inducing the formation of a color in the coloring agent

  when heat is applied to it, these constituents being of general use.

  Usually colorless or lightly colored leuco dyes, which contain a lactone, lactam or spiropyran ring, are used as the coloring agent and organic acids and phenolic compounds are used as the color developer. Heat-sensitive recording materials of this type, which in combination include the above-mentioned dyestuff and color developer, are widely used due to the light colored tint of the images obtained, the high degree of whiteness of the background of the heat-sensitive recording material and the excellent

  weather resistance of images.

  For some time, the application of relatively thick heat-sensitive recording materials to labels, tickets, cards and labels

price is increasing.

  In a conventional recording apparatus for heat-sensitive recording material, the heat-sensitive recording material is held between a thermal head and a pressure roller by applying a

  pressure, for example by a spring, and printing on the recording material

  ment is accomplished while the material is moving between the thermal head and the pressure roller while undergoing pressure To improve the close contact between the thermal head and the recording material, methods have been proposed to improve the surface smoothness of the material. heat-sensitive recording material, as described in Japanese published patent Nos. 52-20,142 and the patent application

  Japanese available to the public N 54-115 255.

  However, in a suitable heat-sensitive recording material

  tional, the support is as thin as a sheet of ordinary paper of general use In the case of a heat-sensitive recording material whose support is relatively thick (hereinafter called thick heat-sensitive recording material), the contact narrow between thermal head and heat-sensitive recording material cannot be improved at high speeds

  printing by simply improving the surface smoothness of the coating material

  registration. The conventional thick thermosensitive recording material generally used at present has the disadvantage that it is difficult to

  put a thermal head in close contact with the surface of the recording material

  This is due to its excessive rigidity, so that irregular or blurred images are formed. In other words, the conventional thick heat-sensitive recording material cannot produce high quality images. To overcome these drawbacks, the present invention aims to provide a thermosensitive recording material allowing excellent close contact with a thermal head, capable of producing excellent images with a high image density, and which does not exhibit the problems associated with

  the irregularity and the blurred aspect of the images.

  This can be achieved by thermosetting recording material.

  sible comprising a support and a heat-sensitive coloring layer formed on the

  support, capable of forming colored images when heat is applied to it

  quée, the rigidity of the recording material in its longitudinal direction according to the Japanese industry standard P-8125 (hereinafter called JIS-P-8125) being less than 4.41 x 10-5 x exp O, 018 x J ( 0.45 exp O,> 18 x gf cm) ox represents the thickness of the recording material, measured according to Japanese industry standard P-8118 (hereinafter called JIS-P-8118), provided that the longitudinal direction recording material either (i) the machine direction corresponding to the longitudinal direction of the cellulose fibers contained in the support, or

  (ii) the direction of the plane of the recording material when a synthetic material

  tick that does not contain fibers oriented in a specific direction is used

for support.

  It is known that the drawbacks of a thermo-recording material

  sensitive thick conventional come from its excessive rigidity According to the

  present invention, because the rigidity of the recording material thermally

  sensitive thick in its longitudinal direction is less than 4.41 x 10-5 x exp O 018 x J (0.45 exp O, 018 x gf cm), x representing the thickness of the recording material, the close contact between the thick heat-sensitive recording material and a thermal head can be improved which allows to obtain high quality images with high image density, and which are

  free from irregularities and blurring.

  In particular, when the heat-sensitive recording material has a thickness greater than or equal to 150 Èm, the problem caused by poor contact with the thermal head can be effectively resolved by lowering the rigidity of the recording material to a value less than

  4.41 x 10-5 x exp 0.0 8 x J (0.45 exp O, 018 x gf cm).

  In the present invention, the rigidity of the heat-sensitive recording material is measured according to JIS-P-8125 and its thickness is measured according to

JIS-P-8118.

  When the stiffness of the recording material in its longitudinal direction is measured, the longitudinal direction of the recording material means (i) the machine direction which corresponds to the longitudinal direction of the cellulosic fibers contained in the support, or (ii) the direction the plane of the recording material when a synthetic material that does not contain fibers

  oriented in a specific direction is used for the support.

  The rigidity of the support usable in the thermosensitive recording material is an important factor for determining the total rigidity of the thick thermosensitive recording material. To lower the rigidity of the thermosensitive recording material in its longitudinal direction, it is therefore desirable to '' use a material with stiffness for the support

  relatively small compared to its thickness A material having a thick-

  sor from 120 to 300 µm and a rigidity of less than 5.19 x 10-5 x exp 0.018 y J (0.53 exp 0.018 Ygf cm), oy is the thickness in uum of the material, is preferably used for the support of thick heat-sensitive recording material according to

the present invention.

  It is also preferable that the thermal recording material

  thick sensitive of the present invention comprises a support of a thick

about 130, um or more.

  When a sheet of paper is used as the support for the thick heat-sensitive recording material, a sheet of paper of desired stiffness can be obtained by controlling the conditions of papermaking, for example by adjusting the amount of filler contained in the paper and the index

  during the preparation of the paper.

  In the present invention, a sheet of paper having a grammage of 100 to 250 g / m 2 is preferably used as a support for the recording material. When the thickness is the same, a sheet is preferred

  higher density paper.

  In addition, it is possible to use a plastic film or a sheet of

  synthetic paper as backing for thermosen recording material

  sible according to the present invention In particular, a synthetic paper is preferred comprising, as main constituent of polyethylene, polypropylene, polystyrene or poly (vinyl chloride) In the case of a plastic film, a film is preferred according to the present invention low density polyethylene, poly (vinyl chloride) or flexible poly (vinylidene chloride), which has a

  modulus of elasticity in relatively low tension.

  In the case where the material used as support is a material of

  high rigidity, rigidity can be lowered by subjecting the material to a calander

  drage, in particular in the case where a sheet of paper is used as support This is due to the fact that the calendering makes it possible to increase the density of the

  paper and therefore lower the stiffness of the paper In addition, the stiffness of the material

  thermosensitive registration can be lowered by subjecting the recording material

  registration to a calendering after the application of the thermosen-

  sible on the support In this case, there is a risk of appearance of a haze on the bottom of the recording material due to calendering, depending on the

  load conditions during the calendering process.

  For this reason, when the heat-sensitive coloring layer is subjected to calendering, it is preferable that the load applied to the recording material is as low as possible. The method for lowering the rigidity of the recording material

  thick heat sensitive is not limited to the above mentioned processes.

  The heat-sensitive recording material according to the present

  invention comprises a support such as a sheet of paper or synthetic paper

  a tick, or a plastic film, and a heat-sensitive coloring layer disposed on the support, which comprises as main constituent a heat-sensitive coloring composition The heat-sensitive coloring composition comprises a coloring agent such as a leuco dye and a color developer capable of inducing the formation of a color in the coloring agent when heat is applied thereto. Furthermore, it is advisable to incorporate a binder in the heat-sensitive coloring layer in order to bond the leuco dye and the color developer to the support of the material. thermosensitive recording of the present invention.

  Any leuco dye used in recording materials

  conventional heat-sensitive can be used as a coloring agent

  for the heat-sensitive coloring layer More precisely, it is used

  in the heat-sensitive coloring layer of triphenyl-

  methane, fluorane, phenothiazine, auramine, spiropyran and indolinophthalide. As color developers which can be used in the heat-sensitive coloring layer, it is possible to use various electron-accepting compounds capable of inducing the formation of a color in the above-mentioned dye leuco-derivatives when heat is applied to them and when they enter in contact with the leuco dyes. Preferably, for example,

  phenolic compounds, thiophenolic compounds, thio- derivatives

  urea, organic acids and their metal salts.

  As binders which can be used in the heat-sensitive coloring layer,

  can use different binders used in thermal recording materials

  conventional mosensibles Specific examples of binders are water-soluble polymers such as polyvinyl alcohol, starch and starch derivatives, cellulose derivatives, sodium polyacrylate and acrylic polyesters.

  In addition, in the present invention, various thermally

  fuses that serve as photosensitizers and various auxiliary additives such as fillers and surfactants, which are used in conventional heat-sensitive recording materials, can be used in conjunction with the leuco dye and the developer

  color in the heat-sensitive coloring layer.

  If necessary, an intermediate layer can be placed between the support and the heat-sensitive coloring layer, and / or a protective layer can

  be provided on the heat-sensitive coloring layer In addition, a coating layer

  magnetic recording may be provided in the thermo recording material

  sensitive, for example when applied to a ticket.

  Other advantages and characteristics of the invention will appear better

  in the following detailed description of embodiments given by way of example

ple only.

Example 1

  Formation of the heat-sensitive coloring layer The following constituents were pulverized and dispersed separately in a sand mill for 2 to 4 h to prepare a liquid A and a liquid B: liquid A Parts by weight

  3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilino-

  fluorane 10 Aqueous solution of poly (vinyl alcohol) at 10% 10 Water 80 liquid B Parts by weight benzyl p-hydroxybenzoate 10 Calcium carbonate 10 2,2 '-methyleneene (4-methyl-6-tert-butylphenol) 5 Solution 10% polyvinyl alcohol aqueous 20 Water 55 Liquid A and Liquid B were mixed with stirring at a weight ratio of 1: 3 to form a coating liquid to form a

heat-sensitive coloring layer.

  The coating liquid to form a heat-sensitive coloring layer was applied to a sheet of commercial paper (manufactured by Chuetsu Pulp Industry Co, Ltd) with a thickness of 256 µm and a rigidity of 372 x 10-5 J ( 38 gf cm) serving as a support, in a dry deposit amount of, 5 g / m 2 by means of a laboratory coating bar, then it was dried.

  thus formed a heat-sensitive coloring layer on the support.

  Formation of a protective layer A mixture of the following constituents was stirred and dispersed to obtain a coating liquid intended to form a protective layer: Parts by weight 10% aqueous solution of poly (vinyl alcohol) 50 Calcium carbonate 2.5 Zinc stearate 0.2 Water 47.3 The coating liquid thus prepared was applied to the heat-sensitive coloring layer formed above in a dry deposit amount of 0.0 g / m 2, then dried to form a protective layer on the coloring layer

  thermosensitive, which made it possible to obtain the recording material thermo-

  sensitive no 1 according to the present invention.

  The thickness and stiffness of the heat-sensitive recording material

  n 1 thus obtained are indicated in table 1.

  Comparative Example 1 The procedure for preparing the heat-sensitive recording material used in Example 1 was repeated except that the support used in Example 1 was replaced by a sheet of paper (manufactured by Shinfuji Paper Co, Ltd) with a thickness of 266 µm and a stiffness of 637 x 10-5 J (65 gf cm) to form the heat-sensitive recording material

comparative only 1.

  The thickness and stiffness of the heat-sensitive recording material

  Comparative # 1 are shown in Table 1.

Example 2

  The same support as the support used in Comparative Example 1, with a thickness of 2661 μm and a rigidity of 637 x 10 -5 J (65 gf cm), was subjected to calendering repeated 4 times at 1 Using a miniicalandre manufactured by Yuri Roll Machine Co, Ltd, a load of 294 N (30 kgf) being applied to the support, so that the thickness and stiffness of the support were reduced respectively to

  234, um and at 294 x 10-5 J (30 gf cm).

  The procedure for preparing the heat-sensitive recording material prepared in Example 1 was repeated except that the support used in Example 1 was replaced by the calendered support above, which made it possible to obtain the material. thermosensitive recording no 2 according to this

invention.

  The thickness and stiffness of the heat-sensitive recording material

  n 2 thus prepared are shown in Table 1.

  Comparative Example 2 The procedure for preparing comparative heat-sensitive recording material No. 1 of Comparative Example 1 was repeated except that the support used in Comparative Example 1 was replaced by a sheet of paper (manufactured by Daishowa Paper Manufacturing Co, Ltd) with a thickness of 232 Ium and a rigidity of 451 x 10-5 J (46 gf cm), which made it possible to obtain the

  No. 2 comparative heat-sensitive recording material.

  The thickness and stiffness of the heat-sensitive recording material

  Comparative No. 2 thus obtained are shown in Table 1.

Example 3

  A heat-sensitive recording material identical to that of

  Comparative Example 1 was prepared.

  The heat-sensitive recording material thus prepared was subjected to calendering repeated six times using a mini-calender manufactured by Yuri Roll Machine Co, Ltd, a load of 196 N (20 kgf) being applied to the heat-sensitive coloring layer , which made it possible to obtain the recording material

  No. 3 thermosensitive according to the present invention.

  The thickness and stiffness of the heat-sensitive recording material

  ne 3 thus obtained are indicated in table 1.

Example 4

  The procedure for preparing the heat-sensitive recording material N 1 of Example 1 was repeated except that the coating liquid A and the coating liquid B used in Example 1 for the preparation of the coating liquid forming the thermosensitive coloring layer were replaced respectively by the following coating liquids C and D, which made it possible to obtain the thermosensitive recording material N 4 according to the present invention: liquid C Parts by weight 3-dibutylamino-6-methyl- 7- anilinofluorane 10 Aqueous solution of poly (vinyl alcohol) at 10% 10 Water 80 liquid D Parts by weight 4- hydroxy-4 '-isopropoxydiphenylsulfone 15 Calcium carbonate 10 Aqueous solution of poly (vinyl alcohol) at 10% 20 Water 55 The thickness and stiffness of the heat-sensitive recording material

  ne 4 thus prepared are indicated in table 1.

  Comparative Example 3 The procedure for preparing the heat-sensitive recording material of Comparative Example 1 was repeated except that the coating liquid A and the coating liquid B used in Comparative Example 1 for the preparation of the liquid of coating forming the heat-sensitive coloring layer were replaced respectively by the coating liquids C and D used in Example 4, which made it possible to obtain the recording material

comparative thermosensitive N 3.

  The thickness and stiffness of the heat-sensitive recording material

  Comparative no 3 thus obtained are shown in Table 1.

Example 5

  The procedure for preparing the heat-sensitive recording material of Example 2 was repeated except that the coating liquid A and the coating liquid B used in Example 2 for the preparation of the coating liquid forming the layer heat-sensitive dye were replaced by the coating liquids C and D used in Example 4, respectively, which made it possible to obtain the heat-sensitive recording material

No. 5 according to the present invention.

  The thickness and stiffness of the heat-sensitive recording material

  N 5 thus prepared are shown in Table 1.

  Comparative Example 4 The procedure for preparing the heat-sensitive recording material of Comparative Example 2 was repeated except that the coating liquid A and the coating liquid B used in Comparative Example 2 for the preparation of the liquid of coating forming the heat-sensitive coloring layer were replaced respectively by the coating liquids C and D used in Example 4, which made it possible to obtain the recording material

comparative thermosensitive N 4.

  The thickness and stiffness of the heat-sensitive recording material

  Comparative N 4 thus obtained are indicated in Table 1.

Example 6

  The procedure for preparing the heat-sensitive recording material N 3 of Example 3 was repeated except that the coating liquid A and the coating liquid B used in Example 3 for the preparation of the coating liquid forming the heat-sensitive coloring layer were replaced respectively by the coating liquids C and D used in Example 4, which made it possible to obtain the heat-sensitive recording material

No. 6 according to the present invention.

  The thickness and stiffness of the heat-sensitive recording material

  No. 6 thus prepared are shown in Table 1.

  Each of the heat sensitive recording materials no 1 to 6 according to the present invention, prepared in Examples 1 to 6, and each of the comparative heat sensitive recording materials N 1 to 4, prepared in Comparative Examples 1 to 4, was subjected a test print using a commercial thermal print tester comprising a thin film print head manufactured by Matsushita Electronic Components Co, Ltd, under conditions where the print speed was 4 ms / line, the density of the dots was 8 points / mm, the density of the lines was 7.7 lines / mm and the electrical energy applied to the thermal head was 0.45 W / point, the width

  pulse increased in steps of 0.2 to 0.9 ms.

  The images thus printed on each recording material

  thermosensitive have been assessed by visual inspection with regard to irre-

  image regularity and image blurring The results are presented in the

table 1 following.

Table 1

  Material thickness Material rigidity Quality of thermo-sensitive image recording (um) 10-5 J (gf cm) Ex 1 261 353 (36) O Ex 2 239 255 (26) O Ex 3 234 225 (23 ) O Ex 4 262 353 (36) O Ex 5 238 264 (27) O Ex 6 236 235 (24) O Ex comp 1 270 608 (62) X Ex comp 2 240 402 (41) A Ex comp 3 269 588 ( 60) X Ex comp 4 238 392 (40) A (*) Image quality: O: excellent (no blurring or irregularities were observed

in the images obtained).

  A: Relatively poor (blurring and irregularity of the images have

more or less observed).

  X: Very poor (blurring and irregularity of the images have been

clearly observed).

  As the results shown in Table 1 show, it is possible to form high quality images free from irregularities and blurring on the heat-sensitive recording material of the present invention Because the rigidity of the heat-sensitive recording material of the present invention is less than 4.41 x 10-5 x exp O, 018 x J (0.45 exp O, 018 x gf cm), ox represents the thickness of the recording material, it is possible to improve the close contact between the thick heat-sensitive recording materials of the

  present invention and a thermal head.

Claims (2)

  1 heat-sensitive recording material comprising a support and a heat-sensitive coloring layer formed on the support, capable of forming a color when heat is applied thereto, characterized in that the rigidity of said heat-sensitive recording material in its longitudinal direction along the JIS-P-8125 standard is less than 4.41 x 10-5 x exp O, 018 x J (0.45 expo, 0 18 X gf cm), ox represents the thickness of said recording material measured according to the standard JIS-P8118, provided that the longitudinal direction of said recording material is (i) the machine direction corresponding to the longitudinal direction of the cellulosic fibers contained in said support, or (ii) the plane direction of said recording material when synthetic material that does not contain fibers oriented in a specific direction is used to said support.   2 heat-sensitive recording material according to claim 1,   characterized in that it has a thickness of 150 yum or more.